Mobile machine with a pressurized tank

ABSTRACT

A mobile machine, in particular an industrial truck ( 1 ), includes at least one pressurized tank ( 3 ), in particular to carry fuel that is in a gaseous state under normal conditions. At least one molding ( 10, 15, 19, 21 ) that is adapted to significant portions of the external contour of the tank ( 3 ) is provided, and which is made of a high density material.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Application No. 10 2005 042938.6, filed Sep. 9, 2005, which application is herein incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a mobile machine, in particular an industrialtruck, with at least one pressurized tank for carrying fuel which is ina gaseous state under normal conditions.

2. Technical Considerations

Mobile machines are frequently operated with fuels that are gaseousunder normal (ambient) conditions. In addition to hydrocarbon-basedfuels, such as propane, butane and methane, increasing use is being madeof hydrogen, which can be used to operate a fuel cell unit, for example.The mobile machine generally has one or more pressurized tanks for thestorage of these fuels. To be able to store the largest possiblequantity of fuel, the tanks are generally pressurized at relatively highpressures, conventionally more than 25 bar and typically on the order ofmagnitude of 200 bar, as high as 350 bar for hydrogen, and, inindividual cases, as high as 700 bar.

In mobile machine applications, an objective is generally to make thecomponents as lightweight as possible so as to increase thecargo-carrying capacity of the vehicle. With fuel tanks of the knownart, attempts have consequently been made to design the fuel tanks sothat they are as lightweight and simultaneously as stable as possible,for which reason aluminum alloys or compound materials can be used. Anadditional objective of tanks of the known art is to achieve maximumfilling pressures and, therefore, maximum filling quantities while usingthe minimum amount of material. As a result of which, the tanks aregenerally cylindrical or spherical in shape. However, tanks of this typeutilize the available space inefficiently, especially if two or moresuch tanks are located next to each other because unused space remainsbetween the tanks or between the tanks and a housing wall, which isgenerally flat and straight. Locating the tank(s) outside the chassis ofthe vehicle, which is frequently done on vehicles that are operated withliquefied natural gas, avoids this problem. However, this has thedisadvantage that the tank(s) are exposed without protection toenvironmental factors, including but not limited to mechanical damageand solar radiation. Also, outboard installation restricts accessibilityto the vehicle and/or the view of the vehicle operator.

Mobile machines with the same basic design are frequently equipped withdifferent propulsion concepts, for example electric propulsion with alead battery or an internal combustion engine with liquid fuels, or anelectric motor with a fuel cell unit and gas fuel, or an internalcombustion engine with gas propellant. One factor, among others, thatdetermines the weight of the vehicle is the weight of the energy storagesystem, for example, the lead battery or the fuel tank. In particular,vehicles with an electric propulsion system and a lead battery arerelatively heavy, given the same operating time. In the case of mobilemachines, this weight is frequently desirable because, on industrialtrucks, for example, the traction is improved or the weight of thebattery can be used to provide a counterweight to the load beingcarried. The heavier the battery, the heavier the load that can becounterweighted by the battery.

On the other hand, vehicles whose energy supply comes from fuel cellsthat are supplied with a gaseous fuel, such as hydrogen, for example,have a significantly lower weight. As a result of which, the usefulload-carrying capacity is reduced, which, in turn, reduces theproductivity of the vehicle. The safety of the vehicle is likewisereduced because, with the same load, the stability is significantly lessthan on an equivalent vehicle equipped with a lead battery.

An object of the invention is, therefore, to create a mobile machine, inparticular an industrial truck, with at least one pressurized tank, inparticular to carry fuel that is in a gaseous state under normalconditions, which has a high level of operational safety and reliabilityand a long period of operation, has a simple construction, makes optimalutilization of space, and makes possible particularly economicaloperation.

SUMMARY OF THE INVENTION

The invention teaches that a molding is provided that is fitted to atleast significant portions of the external contour of the tank, whichmolding is made of a high-density material. “High density”, as usedhere, means a density of greater than 6 kg/dm³, such as greater than 7kg/dm³. The space surrounding the tank, which in conventional systemsgenerally remains unused on account of the complex shape of the tank, isthereby filled with heavy material. In this manner, the traction of thevehicle and its stability are increased significantly. Because thespaces filled by air in vehicles of the known art are occupied by themolding, the safety of the vehicle is also improved in the event ofleaks in the fuel system because there is less ambient air that couldform an explosive or flammable mixture with the fuel.

The molding is advantageously fitted to the contour of the componentsthat surround the tank. The empty space between the tank and thesurrounding components is thereby occupied as fully as possible.

It is also advantageous if the molding is fitted to significant parts ofthe external contour of at least one additional tank. In known systemshaving two or more tanks, the amount of unused space is particularlylarge, especially when the tanks in question are cylindrical orspherical. By fitting the molding of the invention to the contour of thetank, the space between the tanks can be effectively filled.

In one advantageous configuration of the invention, the molding has atleast one recess with at least an approximately circular arc-shapedcross section to hold at least one tank. Tanks generally havecylindrical or spherical external contours, which can be enclosedparticularly firmly in a recess of this type.

It is advantageous if at least one elastic element is located in therecess that holds the tank. The tank is, therefore, not in directcontact with the molding and is vibrationally isolated from it. The wearand abrasion of the molding and the tank in the event of mutual, evenminimal, movements is thereby significantly reduced or even totallyeliminated.

In one advantageous configuration of the invention, the molding can bemade of metal, e.g., a ferrous material, in particular steel or castiron. Ferrous materials are economical, easy to work, and have arelatively high density.

In an additional advantageous configuration, the molding can be formedfrom a lead alloy. Lead has a high density, is relatively economical andeasy to shape, and can be closely fitted to complex geometries.

It is further appropriate if the molding has at least one approximatelyplane (flat) lateral surface. The three-dimensional components of themobile machine and the housings of the mobile machine or of thecomponents used in it generally also have plane surfaces, so that thereis particularly good contact between the plane surfaces and the molding.The introduction of forces is thereby distributed over a large surfacearea, which eliminates harmful peak or spot loads on the molding and/oron the mobile machine and/or on its components.

In an additional advantageous realization of the invention, the moldinghas at least two approximately parallel lateral surfaces. The moldingcan, therefore, be made to fit in the vehicle particularly efficientlybecause there are contact surfaces on two sides that are at a constantdistance from each other.

The molding advantageously has at least one fastening device to connectthe molding with the industrial truck. The molding can thereby befastened in the vehicle using simple means, and the molding can be usedfor the fastening of the tank, which is securely fixed in position onaccount of the matching contour of the molding.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages and details of the invention are explained ingreater detail below on the basis of the exemplary embodimentillustrated in the accompanying drawings. Identical parts are identifiedby the same reference numbers throughout.

FIG. 1 shows a counterweighted fork lift truck as one example of amobile machine of the invention;

FIG. 2 shows two pressurized tanks with three moldings of the invention,and a detail showing two moldings; and

FIG. 3 shows a molding of the invention to hold four pressurized tanks.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a counterweighted fork lift truck 1 with a fuel cell unit 2and a pressurized hydrogen tank 3 as one example of a mobile machine ofthe invention. Loads are held and transported on load-holding means 4(such as forks) that are not shown in any further detail in thedrawings. To compensate for the weight of the load, there is acounterweight 5 in the stem area of the fork lift truck 1. Between afront axle 6 and a rear axle 7 of the fork lift truck 1 there is ahousing compartment 8 that would hold the battery if the fork lift truckwere electrically operated and powered by a battery. In the fork lifttruck 1 shown in the illustration, this housing compartment 8 containsthe fuel cell unit 2, the hydrogen tank 3, and additional auxiliaryunits 9. The hydrogen tank 3 has the basic cylindrical shape that isconventional for such applications in the known art and isadvantageously lightweight for mobile applications, for example as aresult of the use of an aluminum alloy or of a fiber-reinforcedcomposite material and/or, when steel is used, use of a minimal wallthickness.

The hydrogen tank 3 is surrounded by two, high-density moldings 10 ofthe invention, each of which has a recess 11 in the shape of a circulararc that fits the external contour of the tank 3. The moldings 10,therefore, have an essentially rectangular outer cross section, which isinterrupted by the circular arc-shaped recess 11. Sides 12 of themolding 10 that face away from the recess 11 are each flat so that themolding is in contact over a large surface area with a floor 13 and wall14 of the housing compartment 8. Above the tank 3, too, there is a flatsurface 12 a available, on which, in the illustrated exemplaryembodiment, the fuel cell unit 2 is located. The moldings 10 arefastened to the industrial truck 1 by threaded fasteners T, as a resultof which the moldings 10 simultaneously act as a holding device for thetank 3. The fuel cell unit 2 can also be fastened to the moldings 10, sothat no independent fastening device is necessary.

The space in industrial trucks that is occupied by the moldings 10 istypically unused in industrial trucks of the known art so that theweight incorporated in the form of the moldings 10 can be used in itsentirety as an additional counterweight.

FIG. 2 is an overhead view which shows (left) an arrangement of twopressurized cylindrical tanks 3 which are surrounded by moldings 10, 15,and (right) the same arrangement in an exploded view. The molding 15,which is located between the two tanks 3, has two recesses 16 with acircular or arc-shaped cross section, which are located between twoparallel flat sides 17. The moldings 10, which are realized in the formof end pieces, are identical to the moldings 10 illustrated in FIG. 1.Additional tanks 3 can easily be inserted between the two tanks 3 byusing additional moldings 15. With the illustrated moldings 10, 15, whenstandardized tanks 3 are used, a tank system of almost any desiredarrangement and size can be constructed by using two types of moldings10, 15. An additional molding 19, which fits the convex shape of a tankbase 18 and fits between the moldings 10 and 15, can be provided for thevicinity of the tank base 18.

If cylindrical tanks 3 of different lengths are provided, the moldings10, 15 can be manufactured in the form of yard goods and cut to fit. Itis also conceivable, however, that moldings 10, 15, with a length thatis less than or equal to the length of the shortest tank 3 being used,can be placed one behind another and cover tanks 3 of any desiredlength.

Elastic support elements 20, which can be made of rubber or a polymermaterial, for example, can be located in some or all of the recesses 11,16. These support elements 20 dampen impacts and vibrations. The wear ofthe tanks 3 and of the moldings 10, 15 is reduced because the tanks 3and moldings 10, 15 are not in direct contact with one another and,therefore, cannot rub against one another. If the moldings 10, 15 arepressed against one another, the tanks are effectively prevented frommoving in their longitudinal direction so that additional securing meansare unnecessary.

FIG. 3 is a schematic illustration of a molding 21 to hold four tanks 3in a configuration that differs from the configuration illustrated inFIG. 2. In this case, not only can the tanks 3 be arranged in a linearrow but a tank system can also be used that extends in two dimensions A,B and is stabilized by the arrangement of recesses 22 in the molding 21.The arrangement can thereby be terminated by means of moldings 10 thatare realized in the form of end pieces, one of which is shown in FIG. 3.The moldings 10, 15, 21 can be fastened to one another either bysuitable fastening devices of the known art that are integrated into themoldings, such as threaded fasteners or slots or grooves and slidingblocks that are introduced into them, and/or by holding the moldings 10,15, 21 together by means of straps, just to mention a few.

It goes without saying that other realizations of the moldings 10, 15,21 are conceivable, for example in the form of a molding that completelysurrounds the tank 3. In such an arrangement, the tank 3 is providedwith optimal protection, although the installation and the replacementof the tank 3, if necessary, are significantly more difficult comparedto the illustrated variant. Depending on the specific requirements, themoldings 10, 15, 21 can be made of a ferrous material, such as grey castiron, for example, or steel, and/or of lead or a lead alloy or anothermaterial of sufficiently high density. Lead and lead alloys arecharacterized by their high density and easy deformability. However, ifthe moldings 10, 15, 21 are required to absorb and/or transmit largeforces, for example because additional components are fastened to them,a steel construction is preferable.

It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. Accordingly, theparticular embodiments described in detail herein are illustrative onlyand are not limiting to the scope of the invention, which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof.

1. A mobile machine, comprising: at least one pressurized tank to carryfuel that is in a gaseous state under normal conditions; and at leastone molding configured to be fitted to significant portions of anexternal contour of the tank, wherein the molding is made of a highdensity material.
 2. The mobile machine as claimed in claim 1, whereinthe molding is also fitted to a contour of components that surround thetank.
 3. The mobile machine as claimed in claim 1, wherein the moldingis fitted to significant parts of an external contour of at least oneadditional tank.
 4. The mobile machine as claimed in claim 1, whereinthe molding has at least one recess with a curved cross section to holdat least one tank.
 5. The mobile machine as claimed in claim 4,including at least one elastic element located in the recess to hold thetank.
 6. The mobile machine as claimed in claim 1, wherein the moldingis made of a ferrous material.
 7. The mobile machine as claimed in claim1, wherein the molding is made of a lead alloy.
 8. The mobile machine asclaimed in claim 1, wherein the molding has at least one approximatelyflat lateral surface.
 9. The mobile machine as claimed in claim 1,wherein the molding has at least two at least approximately parallellateral surfaces.
 10. The mobile machine as claimed in claim 1, whereinthe molding has at least one fastening device for connection of themolding with the mobile machine.
 11. The mobile machine as claimed inclaim 2, wherein the molding is fitted to significant parts of anexternal contour of at least one additional tank.
 12. The mobile machineas claimed in claim 2, wherein the molding has at least one recess withan at least approximately arc-shaped cross section to hold at least onetank.
 13. The mobile machine as claimed in claim 1, wherein the moldingis made of steel or cast iron.
 14. The mobile machine as claimed inclaim 1, wherein the molding includes at least one recess having asurface complementary to an outer surface of the at least one tank, withat least one elastic element located in the recess and configured tocontact the tank.
 15. The mobile machine as claimed in claim 2, whereinthe molding includes at least one recess having a surface complementaryto an outer surface of the at least one tank, with at least one elasticelement located in the recess and configured to contact the tank. 16.The mobile machine as claimed in claim 3, wherein the molding includesat least one recess having a surface complementary to an outer surfaceof the at least one tank, with at least one elastic element located inthe recess and configured to contact the tank.
 17. The mobile machine asclaimed in claim 1, wherein the molding includes at least onesubstantially flat outer surface.
 18. The mobile machine as claimed inclaim 14, wherein the molding includes at least one substantially flatouter surface.